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Standard Specification for Quenched and Tempered Steel Bolts and Studs. Covers chemical and mechanical requirements for two types of quenched and tempered steel bolts, intended for general high-strength applications.
ASTM Hex Bolt is manufactured to the standard specification for quenched and tempered steel bolts and studs. It covers the chemical and mechanical requirements for two types of quenched and tempered steel bolts, studs, and threaded fasteners for general high-strength applications.
Standard update: Since 2016, ASTM A325 and A490 have been consolidated into ASTM F3125, which also covers A325M, A490M, F1852 and F2280. QS Fastener can certify against both the legacy A325 / A490 documents and the current F3125 specification.
TYPE 1
Medium carbon or alloy steel bolts and studs, manufactured from 1/4" to 3" (imperial) and M6 to M76 (metric), suitable for general high-strength structural bolting.
TYPE 2
Low carbon martensite steel bolts and studs, manufactured from 1/4" to 1" (imperial) and M6 to M24 (metric), for weight-sensitive applications.
For ASTM A325 structural bolting, the active types are Type 1 (medium carbon, carbon boron, or medium carbon alloy steel) and Type 3 (weathering steel). A325 Type 2 was withdrawn in 1991; equivalent low-carbon martensite options remain available on request.
QS Fastener manufactures both Type 1 and Type 2 ASTM Hex Bolts with fine precision and full EN 10204 Type 3.1 certification. All products are dimensionally inspected, hardness-tested, and mechanically verified before dispatch.
✓ EN 10204 Type 3.1
Chemical, mechanical and heat/lot traceability per shipment.
✓ Verified quality
Dimensional, hardness and mechanical testing before dispatch.
✓ Rolled threads
Threads are roll-formed after heat treatment for fatigue resistance.
✓ OEM support
Custom labels, barcodes, and packaging available.
01 / STRUCTURAL STEEL
Bridges, building frameworks, towers, and high-load bolted connections.
02 / PETROCHEMICAL
Pressure vessels, piping flanges, heat exchangers, and refinery equipment.
03 / WIND ENERGY
Tower flange connections, nacelle mounting, and blade root fastening.
04 / INFRASTRUCTURE
Railway track fastening, tunnel brackets, highway barriers, and crane rails.
05 / OIL & GAS
Offshore platform connections, subsea flanges, and wellhead equipment.
06 / HEAVY EQUIPMENT
Excavators, mining trucks, crushers, and conveyor systems.
| Material Type | Key Composition | Hardness |
|---|---|---|
| Medium Carbon Steel | Type 1: C 0.28-0.55%, Mn 0.60-1.00% | HRC 25-34 |
| Alloy Steel (4140 / 4340) | Type 1: Cr 0.80-1.10%, Mo 0.15-0.25% | HRC 32-39 |
| Low Carbon Martensite Steel | Type 2: C 0.15% max, Ni 3.5-5.0% | HRC 30-38 |
| Stainless Steel (304 / 316) | Option: Cr 18-20%, Ni 8-14% | HRB 80-95 |
| Copper / Brass | Option: Cu 99% min / Cu 60-70%, Zn 30-40% | HRB 50-80 |
Black Oxide
Mild corrosion resistance, matte appearance.
Salt spray 12-24 h
Zinc Plating
Blue / yellow / black passivation.
Salt spray 48-200 h
Hot-Dip Galvanizing (HDG)
Thick bonded coating for outdoor use.
Salt spray 500+ h
Plain / Self-Colour
Degreased and oiled only, for indoor use.
Dacromet / Geomet
Chromium-free flake coating.
Salt spray 720+ h
Phosphate & Oil
Improved break-away torque consistency.
Salt spray 24-72 h
A490 coating note: Per ASTM, A490 bolts must not be hot-dip galvanized, mechanically deposited, or electroplated with zinc because of hydrogen embrittlement risk. Approved corrosion protection includes zinc/aluminum flake coating per ASTM F1136 Grade 3 (Geomet).
| Grade | Specification | Size Range | Proof Load (ksi) | Tensile (ksi) | Yield (ksi) | Hardness |
|---|---|---|---|---|---|---|
| Grade 5 | SAE J429 | 1/4" - 1" | 85 | 120 | 92 | HRC 25-34 |
| Grade 5 | SAE J429 | Over 1" - 1-1/2" | 74 | 105 | 81 | HRC 19-30 |
| Grade 8 | SAE J429 | 1/4" - 1-1/2" | 120 | 150 | 130 | HRC 33-39 |
| A325 Type 1 | ASTM F3125 (legacy A325) | 1/2" - 1-1/2" | 85 | 120 / 105 | 92 / 81 | HRC 24-35 |
| A325 Type 3 | ASTM F3125 (weathering steel) | 1/2" - 1-1/2" | 85 | 120 / 105 | 92 / 81 | HRC 24-35 |
| A490 | ASTM F3125 (legacy A490) | 1/2" - 1-1/2" | 120 | 150 / 140 | 130 / 120 | HRC 33-38 |
| B7 | ASTM A193 | Up to 2-1/2" | - | 125 | 105 | 35 HRC max |
| B8 Class 1 (304) | ASTM A193 | All sizes | - | 75 | 30 | 96 HRB max |
| B8M Class 1 (316) | ASTM A193 | All sizes | - | 75 | 30 | 96 HRB max |
Values are minimum requirements per the cited specifications. A325 tensile and yield values are shown for 1" max and over 1" diameters. A193 B7 values are shown for diameters up to 2-1/2".
SAE J429 Grade 5
Three radial lines on the head, spaced 120 degrees apart.
SAE J429 Grade 8
Six radial lines on the head, spaced 60 degrees apart.
F3125 Grade A325
Head marked "A325" plus the manufacturer symbol.
F3125 Grade A490
Head marked "A490" plus the manufacturer symbol.
ASTM A193 B7
Head marked "B7" plus the manufacturer symbol.
ASTM A193 B8 / B8M
Head marked "B8" or "B8M" plus the manufacturer symbol.
ASTM A193 / A320ASTM F3125 (A325 / A490)ASME B18.2.1ASME B1.1ISO 898-1ISO 4014DIN 931 / DIN 933EN 14399
ASTM F3125, issued in 2016, consolidates A325, A325M, A490, A490M, F1852 and F2280. A325 and A490 are now grades under F3125.
| Imperial Size (UNC) | Metric Size | Pitch |
|---|---|---|
| 1/4" | M6 | 1.0 mm |
| 3/8" | M10 | 1.5 mm |
| 1/2" | M12 | 1.75 mm |
| 5/8" | M16 | 2.0 mm |
| 3/4" | M20 | 2.5 mm |
| 7/8" | M24 | 3.0 mm |
Threads conform to the Unified Coarse Thread (UNC) series for imperial bolts and ISO metric coarse for metric bolts, manufactured to Grade 2A accuracy per ASME B1.1. For coated fasteners, allowance is provided so coated threads remain within specified limits. Per ASTM A193, traditional applications above 1 in. diameter commonly specify 8 threads per inch (TPI).
Kraft boxes
With inner partitions, thread protection and full labeling.
Bulk cartons
Five-layer corrugated, waterproof sealed and strapped.
Pallets / wooden cases
ISPM-15 heat treatment certification available.
Resealable polybags
For samples and low-volume orders.
VCI anti-rust packaging
For long-distance overseas shipment.
Custom OEM packaging
Labels, barcodes and packaging; MOQ may apply.
01 Raw Material Inspection
02 Wire Drawing
03 Cold / Hot Heading
04 Thread Rolling
05 Heat Treatment
06 Surface Finishing
07 Dimensional Inspection
08 Mechanical Testing
09 Final Cleaning
10 Oiling / Preservative
11 Packaging & Labeling
12 Outgoing QC
Dimensional inspection
Head height, width across flats, thread pitch, thread length and overall length per ASME B18.2.1.
Mechanical testing
Tensile, yield, elongation, reduction of area, proof load and hardness.
Non-destructive testing
MPI on critical grades, ultrasonic for larger diameters.
Chemical analysis
OES or combustion analysis per material certificate.
Coating thickness
Magnetic or eddy-current per ASTM B499; salt spray per ASTM B117.
Final verification
100% visual inspection, GO/NO-GO thread check and traceability.
1. What is the difference between ASTM A325 and A490 bolts?
A325 bolts are medium carbon steel with 120 ksi (1" max) / 105 ksi (over 1") minimum tensile and 92 / 81 ksi minimum yield. A490 bolts are quenched and tempered alloy steel with 150 ksi (1.5" max) / 140 ksi (over 1.5") minimum tensile and 130 / 120 ksi minimum yield, and they require hardened washers. Since 2016, both are grades within ASTM F3125.
2. Do you supply bolts certified to ASTM F3125?
Yes. A325 and A490 are now grades within ASTM F3125, which consolidated A325, A325M, A490, A490M, F1852 and F2280 in 2016. We issue certificates to the current F3125 document or the legacy A325 / A490 documents as required.
3. Can A490 bolts be hot-dip galvanized?
Per ASTM, A490 bolts must not be hot-dip galvanized, mechanically deposited, or electroplated with zinc due to hydrogen embrittlement risk. Approved corrosion protection includes zinc/aluminum flake coating per ASTM F1136 Grade 3 (Geomet); for hot-dip galvanized structural bolting, specify A325 or F3125 Grade A325.
4. Can you provide MTR with each shipment?
Yes. EN 10204 Type 3.1 certificates are standard; Type 3.2 third-party witnessed available on request. Each includes chemical composition, mechanical test results, and heat/lot traceability.
5. What is the typical lead time?
Standard sizes (1/4"-1"): 15-25 working days. Non-standard sizes or custom finishes: 25-40 working days. Urgent orders can be expedited.
6. Do you offer hydrogen embrittlement relief baking?
Yes. For Grade 8+ bolts with acid pickling or electroplating, we perform relief baking per ASTM F1940 (190-220 C for 4-24 hours).
7. What is the MOQ?
Stock sizes (1/4"-3/4"): 2,000 pcs per size. Larger or non-standard sizes: please inquire. Samples (50-200 pcs) are available for testing.
8. How do you ensure thread quality?
Threads are roll-formed after heat treatment for fatigue resistance. Every lot is sample-tested with GO/NO-GO gauges per ASME B1.1 and B1.16M.
9. How can I identify the grade of a hex bolt?
SAE J429 Grade 5 heads carry three radial lines, while Grade 8 heads carry six radial lines. A325, A490, B7 and B8 / B8M bolts carry the specification marking plus the manufacturer symbol on the head.
